The present invention relates to a disc brake assembly for wheeled vehicles, and more particularly to a disc brake assembly of the pin slide type which includes a stationary support member mounted on a vehicle body structure, a caliper member axially slidably mounted on the stationary support member, and at least one support pin fixed to either the stationary support member or the caliper member and slidably inserted into an axial bore in the other member for slidable support of the caliper member.
In such a disc brake assembly, a sealing boot is arranged in surrounding relationship with the support pin to hermetically close an annular opening between the support pin and the axial bore. The conventional sealing boot includes a bellows portion which is integrally formed at the opposite ends thereof with an outside cylindrical sealing portion coupled over the support pin and an inside cylindrical sealing portion coupled within an annular groove in the other member. The inside cylindrical sealing portion of the bellows portion acts to prevent entry of water and dirt into the sealing boot and to absorb vibration acting thereto from the caliper member during travel of the vehicle on a rough road. In the case that the caliper member is heavy in weight for use in a heavy vehicle such as a truck, the inside cylindrical sealing portion of the boot may not be deformed in response to vibration of the caliper member. If the sealing portion is greatly deformed in a moment, the outer circumference of the sealing portion will be separated from the bottom surface of the annular groove to allow water and dirt to be sucked into the sealing boot. Although such a problem can be solved by enlarging the interference of the sealing portion, the assembling work of the sealing portion becomes difficult, and the sliding resistance of the caliper member increases, resulting in defacement of the sealing portion in a short period of time.